Re–Os results from ODP Site 801: Evidence for extensive Re uptake during alteration of oceanic crust

Recycling of oceanic crust from a stagnant slab in the mantle transition zone: Evidence from Cenozoic continental basalts in Zhejiang Province, SE China

“…Because even minor amounts of crustal contamination can significantly increase the Os isotopic composition of basaltic magma without a significant increase in the Os contents (Lassiter and Luhr, 2001;McBride et al, 2001;Reisberg et al, 2008;Xu et al, 2007), the observed composition of the Zhejiang basalts are not due to crustal contamination. Thus, the most likely explanation for the Re/Os and 187 Os/ 188 Os ratios of the basalts is derivation from ancient, recycled oceanic crust to which sea water has been added.…”

Chemical and chronologic complexity in the convecting upper mantle: Evidence from the Taitao ophiolite, southern Chile

“…Yet certain processes involving high fluid-rock ratios have been shown to cause at least moderate fractionations in the relative abundances of the HSE, and possibly even 187 Os/ 188 Os of peridotites (Brandon et al, 1996;Walker et al, 2007). Further, given that there are large differences among the concentrations of the HSE in seawater (e.g., Colodner et al, 1993;Anbar et al, 1996), and that the Os isotopic composition of seawater is much more radiogenic than typical mantle materials (e.g., Sharma et al, 1997), it is conceivable that water-rock reactions involving seawater could also lead to modifications of HSE abundances and Os isotopic compositions in affected rocks, especially those with low concentrations of the HSE, such as the mafic rocks (Blusztajn et al, 2000;Peucker-Ehrenbrink et al, 2003;Reisberg et al, 2008).…”

Composition of the Oceanic Crust

“…Since abyssal peridotites presumably represent the residues of mantle that melted to produce MORB, this difference presents something of a conundrum and contrasts with Nd isotopes, which are largely similar in MORB and abyssal peridotites (e.g., Cipriani et al, 2004; 1994), although the peridotites do extend to somewhat more depleted Nd isotopic compositions (Warren et al, 2009 , 1998). Re can also be taken up by basalts during hydrothermal alteration, which will, in turn, quickly lead to radiogenic Os isotopic compositions (Reisberg et al, 2008 Os fail to fully equilibrate with the melt. This interpretation is supported by work of Burton et al (1999), who showed that silicate minerals and interstitial sulfides in a Kilbourne Hole peridotite were in isotopic equilibrium with each other but were out of equilibrium with sulfide inclusions inside silicates and which had much less radiogenic Os.…”